Cooling system



Aug. 13, 1929.

/ A. G. M.- MICHELL COOLING SYSTEM s Sheets-Sheet Original Filed June29, 1925 3 Shee ts-Sheet A. G. M. MICHELL COOLING SYSTEM Original FiledJune 29 1923 Aug. 13, 1929.

Aug. 13, 1929. v Re 17,401

A. g. M. MICHELL COOLING SYSTEM 25 By this sam'e'and before proceedingto specify the Reissued' Aug. 13, j

[UNI ED STATES ,PIATENTO OFF-Ice. t

ANTHONY GEORGE MALDON MICHELL, OF MELBOURNE, VICTORIA, AUSTRALIA, AS-SIGNOB, BY MESNE 'ASSIGNMENTS, TO MICHELLCRANKLESS ENGINES CORPORA-TION, OF NEW YORK, N. Y., CORPORATION OF NEW YORK. v

' co'onme sYs'rErL Original Ito. 1,621,943, dated March 22, 1997, Serial190.6%,543, filed June 29, 1923, and in Australia Application forreissne filed March 22, 1929. Serial No. 349,214;

July 18, 1922.

- The purpose of the present invention is to securemore efficientcooling by ai r cur:

rents of the cylinders, pistons and other working parts of machinesoperating with hot working fluids particularly internal combustionengines,'the invention being also series of ducts communicating with theat-' mosphere and the channels between said fins, whereby a plurality ofair channels are provided, fed continuouslv'with fresh air, the

feed being created either by .a fan or sue-v p tion from the exhaustpressure of the engine. i

In the suggestions hitherto advanced for carrying out this method of aircooling the essential factors governing the practical application ofsame have not been stated or enlarged upon with a view to ascertainingan efiicient arrangement of the air channels. invention it is sought toachieve improvements according to this-invention thefundamentalconsiderations in the rational design of an air cooling system Wlll.

0 be stated.

The tenor of the calculations is as follows:

The main data of the problem are: (A) The quantity of heat which must bedissipated per unit time in order to maintain asteady temperature (B)the Earea of surface of the hot body which can be made available forconduction of heat to the air;

the difference of temperature between the hot body and the air; (thisdifference be ng 40 dependent on the temperature of the air,

and the maximum permissible steady temperature of the cylinder or otherhot body) (D) the permissible rate at whichenergy may be expended inmoving the cooling air for the purpose of bringing it into contact withthe body. (A), (B) and (C)-jointly determine the velocity with which airmust be caused to flow over the surface of the body, the rate ofconduction of heat being known to vary approximately as the threefourthspower of the velocity of' the air. j

current of cooling air. increase of temperature to the initialdifferchiefly contemplated .This velocity jointly with determines themaximum quantity of "air which can-be clrculated, and the latterquantity jointly with (A) determinesa minimum increaseof temperaturewhich must be given to the The ratio of such ence between thetemperatures of the hot body and cooling air determines, from knownexperimental laws, the ratio'of the transverse dimensions of the airchannels to their efi'ectivelength. By effective length of an 'airchannel is meant its length in the direction of a stramof air from theplace where the stream enters the channel to the lace where it leaves.

The velocity and quantity of air, already assigned, jointly determinethe total sectional area of these channels while their number andindividual dimensions are settled by practical considerations as toeconomical processes of workmanship having regard to the materials "tobe applied."

In this way, there are for each class of materials limitations to theappropriate transverse dimensions and effective lengths of the airchannels. For the best results it is usually desirable that the ratio ofthe effective length of the channel to its width should be of the orderof 20 or 30 and a leading objectof the present invention is to securesuch a ratio. without incurring difliculties of construction. In thecase of cast iron cylinders of ordinary dimensions andas ordinarilyconstructed theappropriate channels are of comparatively largetransverse dimensions and their effective lengths, deduced by theprocess outlined above, may be such that each channelex'tends'throughout the length or circumference of the cylinder. In the,case, however, of cylinders of forged steel or similar materials, suchas are in the present design, the formation of such relatively.largeichannels 18 very wasteful and expensive, and

channels of relatively small section beingadopted, the process ofcalculation above exthe use of channels whose plained requires Vefiecti've length is, small in roportion to the length or circm'nferenceo the cylinder.

leading purpose of the present invenv tion is to provide modes ofconstruction and arrangement of. air-channels suitable for forgedcylinders of internal combusion e11- ginesand in accordance with theprinciples above set forth.

As above stated the ratio of the effective length of such channels totheir width or smaller transverse dimensions, is of the order internalcombusion engine of the crankless.

" type, described in United States patent spec- 'tant from it.

ification No. 1,409,057, the section being taken on the lines DEF ofFig. 2 or ABC of Fig. 3 and passing through both the axis XX of theengine shaft, and the centre line YY of one of the cylinders;

Fig. 2 is a,cross section of one of the cylinders on the line G, G ofFig.1;

Fig. 3 1s a similar cross section on the line H, H of Fig. 1;

Fig. 4 is a diagrammatic view of air channels; and

Fig. '5 is a relatively enlarged view showing details of one channel.

As shown in Figs. 1, 2 and 3 the cylinder 1, whose centre-line is YY,contains a piston 2, in the form of a thin cylinder closed by theend-piece 3, and diaphragm 4, the latter carrying the slipper-cup 5 andslipper G.

The latter makes contact with the swashplate-or slant 7, fixed on theshaft 42 whose centre-line is XX.

In these features, and in its general.m0de of operation the engine is inaccordance with Patent 1,409,057 of above cited. Usually severalcylinders are arranged circumferentially around the shaft 42, being allequidis- The cylinder 1, is fitted with exhaust valve 8,-and inductionvalve 9 the latter being contained in an induction branch 10 connectingwith the induction chamber 11, communicating with main induction pipe12. The actuating mechanism of the-valves, the ignition apparatus andother accessories are not shown, the following description and thedrawings being restricted to such matters as are necessary for the clearunderstanding of the nature of the invention, i. e. the improved meansof air cooling.

The walls 13, 14 of the cylinder 1, and its combustion chamber, areformed as shown in Figs. 1 and 5 with relatively thin and is a mantle,comprising a thin shell 16 enclosing the fins, and an external jacket17, the latter being formed in a number of segments 18 between thejackets 17 to the atmos phere. The jackets and shell may be secured tothe cylinder 1, by circumferential screwed bars 20, 21 withsaddle-pieces 22 or other suitable means (see Fig. 2).

At the outer end of the cylinder the jacketducts 19,, merge into acommon outlet consisting' of a circular cowl or short pipe 23, coaxialwith the cylinder 1, and surrounding the central exhaust valve 8. Thewall 24 of this pipe is continuous circumferentially being formed as acontinuation of the peripheral walls of the jackets 17. The interspaces18 are closed at their outer. ends by cross walls 25, so that no directcommunication exists from the atmosphere into the pipe 23. The ducts 19on the other hand terminate at the opposite or inner end of thecylinders, being preferably of continuously diminishing radial width inthis direc-' tion whereby the velocity of the air past the whole of theslots 18 is maintained more or less uniform.

The exhaust valve 8, has its stem 8 and spring 28 supported in a cage29, which is preferably integral with the ring 30 which forms theexhaust port, being united thereto by webs 31, and furnished with wings32, (which may be formed as extensions of the webs) extending radiallybeyond the ring 30, into the path of thea-ir flow from the ducts 19 andthereby acting as cooling fins for the exhaust valve casing 29. Thespring 33 of the induction valve 9 is external to the pipe 23 as shown(see Fig. 1).

In order to. draw an effective current of cooling air through the systemof pipe 23, ducts 19, slots 18 and 18, and channels 15, a fan 35,havingblades 36 may be employed. This fan may be mounted directly on theshaft 42, so as to be rotated thereby, and a shroud ring 37 anddiaphragm plate 38 may be provided to enclose the pipes 23 of all thecylinders (arranged, as above indi-.

cated, ina-circumferential series) and thus exclude all means of ingressof air, other than that through the passages above mentioned from theatmosphere to the inlet side of the fan.

The action of the 'fan in. inducing the desired current, of air isassisted by the ejector action of the exhaust gases issuing from thering 30, into the pipe 23, the action of these parts being similar tothose of the exhaust, nozzle and blast pipe of a steam radius of the fanand its axial distance from.

the centre of the machine, a light weight attached to its periphery isrelatively Very effective for this purpose, and by this arrangement alarge deduction from the weight of the slant otherwise necessary may bemade. i

In order to effect cooling of the piston, which as above stated ispreferably constructed-as a thin cylinder and consequently incapableottransmitting heat at a suflicient rate by metallic conduction, it ismade fluid tight by welding or otherwise hermetically joining the endpiece 3-, and diaphragm 4 to the cylindrical body, and a quantity of asuitable conductive liquid, e. g. mercury is enclosed within it. A plug41, is provided for introducing this liquid which is thrown from end toend of the hollow piston as the latter reciprocates; The end-piece 3 anddiaphragm 4 are respectively made convex and concave on their interiorsides, so as to effectively distribute the liquid over the surface ofthe former and of the cylindrical body of the piston as indicated by thedotted lines in Fig. 1.

The use of mercury in a hollow piston as a cooling agent has beenpracticed or proposed in connection with cylinders cooled by othermethods but the application of such cooling agent has a specialappropriateness and function in cooling thehead of a long cylindricalhollow piston of the form de scribed, the heat being thus transferredfrom the head of the piston to'its cylindrical wall, and thence to thecorresponding wall of the cylinder, the latter being air-cooledthroughout its length. I claim:

1. In a c linder cooledby circulation of air, multip e channels formedcircumferent-ially around the cylinder and having each a plurality oflateral inlets alternating with a corresponding plurality of lateraloutlets for the circulating air, each inlet and outlet, slot common to aplurality of channels, the length of each channel between inlet andoutlet being many times greater than its smaller transverse dimension.

2. In a cylinder cooled by circulation of air, a plurality ofcircumferential fins formingbetween them narrow channels, and acylindricalshell enclosing the latter and m which is formed a pluralityof, narrow longitudinal inlet slots alternating with a correspondingplurality of narrow outlet slots, each" slot being common tosubstantially all the channels.

3. A cylinder to be air-cooled. having a series of narrowcircumferential channels formed thereon, longitudinal-air ductstransverse to said channels, and a cylindrical covering shell formedwith a series of longitudinal slots making communication between thechannels and the air ducts.

.4. In a cylinder cooled by circulation of air, a pijlrality ofcircumferential fins enclosing tween them a corresponding plurality ofnarrow circumferential channels, and a cylindrical shell enclosing thelatter and in which is-formed a plurality of narrow longitudinal inletslots and a plurality of narrow longitudinal outlet slots extendingacross the fins, each of the latter opening laterally into alongitudinal duct conveying the air from such outlet.

5. Means for cooling aplurality of cylinrders grouped circumferentiallywith parallel axes, consisting of a plurality of mantles enclosing eachof the cylinders, and through which the circulated air enters radiallyto each cylinder from the external atmosphere, and from which it isdelivered longitudinally into a common outlet casing.

6. The combination of an engine cylinder, a plurality of circumferentialfins forming channels surrounding the cylinders, a hollow jacket for thefins, having a plurality of longitudinal slots for admitting air to saidchannels, said jacket having longitudinal openings in its inner wallbetween said slots to admit air to the interionof the jacket from saidchannels.

7. The combination of an engine cylinder, a plurality of circumferentialfins formingchannels surrounding the cylinders, a hollow jacket for thefins having a plurality of longitudinal slots extending across the finsfor admitting air 'to said channels, said jacket having longitudinalopeningsin its inner wall between said slots to admit air to theinterior of the jacket from said channels,

means closing the longitudinal slots at one a plurality ofcircumferential fins, forming channels surrounding-the cylinders, ahollow jacket for the fins having a lurality of longitudinal slots, eachfor admitting air to all of said channels,'said jacket havinglongitudinal openings in its'inn'er, wall between saidslots to admitair-to the interior of the jacketfrom said channels, means closing theongitudinal slots at one end, and an outlet casing communicating withthe interior of the jacket, and means for creating a suction in thecasing.

9. The combination with an'engine cylinder of peripheral cooling finsthereon, a holtending across the fins, and chambers cover-' low jacketfor said fins open at its discharge end and having longitudinal'entranceslotsand exit slots therein exposing said fins to the interior of saidjacket, both slots extending across the fins, and an exhaust fancooperating with the open end of said jacket.

10. The combination with an. engine cylinder, of peripheral cooling finsthereon, a hollow jacket for said fins and having longitudinal entranceslots extending across the fins to supply air to said fins and alterringinclosing a chamber between said cylinder and fan, an an exhaust valvedischarging into sald chamber.

11. The combination with an engine cylinder having closely arrangedcooling .fins thereon; of a thin mantle surrounding said fins andprovided with parallel longitudinal slots crossing the fins, and ajacket having portions arranged between the slots in the mantles to forminlet slots for air, said'po rtions connected by cross walls, and a fanto exhaust one end of said jacket, whereby air will enter through the.inlet slots into the narrow peripheral channels between said fins andpass only partially around the circumference of the cylinder between thefins, through the slots in the mantle into the interior of the jacketfor exhaustby said 'fan in substantially separate currents;

12. The combination with an engine cylinder having closely arrangedperipheral cooling fins thereon; of a thin mantle contacting with theedges of the fins and having longitudinal slots therein extending acrossthe fins, a jacket surrounding the mantle having longitudinal slots alsoexing the slots in the mantle of considerably greater peripheral widththan the slots in the mantles.

13. Inan air cooled engine, a cylinder having cooling means thereabout,means dividing said cooling means into a plurality of peripherallyseparated segmental ortions, and independent means exten inglongitudinally of the cylinder substantially throughout the lengththereof for conducting cooling air to said segmental portions.

14. In an air cooled engine, a cylinder having cooling means thereabout,means dividing said cooling means into a plurality of peripherallyseparated segmental portions, and independent peripherally separatedmeans extending longitudinally of the cylinder for conducting coolingair to said segmental portions.

15. In an air cooled engine, a cylinder having peripheral air coolingfins thereon extending around the cylinder, and a plurality ofperipherally spaced means extending longitudinally of the cylindersubstantially throughout the length thereof for conducting said fins.

16. In an air cooled engine, a cylinder having. a plurality ofcircumferential channels formed thereon extending around the cylinder, aplurality of peripherally disposed means having separated portionsextending longitudinally of the cylinder substantially throughout thelength. thereof for conducting air to said channels, and peripherallydisposed means having separated portions for conducting the heated airfrom said channels. 17. In an air cooled engine, a cylinder having aplurality of circumferential channels formed thereon, a plurality ofperipherally disposed means having separated portions for conducting airto said channels, and peripherally disposed means having separatedportions alternating in location around the cylinder wall with saidfirst named means for conducting the heated air from said channels.

18. In an air cooled engine, a'cylinder, a

plurality of spaced, substantially parallel cooling fins surrounding thecylinder wall, a plurality of passages extending longitudinally of thecylinder for conducting cooling air to the cylinder wall and fins, and aplurality of passages extending longitudinally of the cylinder forconducting air away from said fins and cylinder wall.-

19. In an air cooled engine, a cylinder, a plurality of spaced,substantially parallel cooling fins surrounding the cylinder wall, a

cooling air to segmental portions of plurality of passages extendinglongitudi-

